Prince William's rare public display of affection following emotional speech

Prince William made an emotional speech at the launch of the National Emergencies Trust in London on Thursday.

The Duke of Cambridge was joined at the last minute by wife Kate Middleton for the outing at St Martin-in-the-Fields in Trafalgar Square.

The couple met with survivors of recent Grenfell Tower disaster, London Bridge terror attacks and the 7/7 London bombings in 2005.

The Duke of Cambridge was joined at the last minute by wife Kate Middleton for the outing at St Martin-in-the-Fields in Trafalgar Square (PA/AAP)

Prince William took to the microphone to give an emotional speech, praising how the UK assists when disaster strikes overseas before launching the initiative which brings together a multitude of charities for when the emergencies are closer to home.

"Just now and on previous occasions, it has been humbling to speak to survivors of the London Bridge and Manchester attacks, the Cumbria floods, the Grenfell Tower fire and other disasters here in the UK," the second-in-line to the throne said.

"Their stories are as heart-breaking as they are inspiring.

Prince William took to the microphone to give an emotional speech at the launch of the National Emergencies Trust (PA/AAP)

"Their resilience and strength are deeply humbling.

"In talking to survivors, I've always been inspired to hear about the help they were offered by people and organisations acting on their own initiative with immediate and heartfelt compassion.

Prince William also praised children "who empty their piggy banks", people who donate blood and families who give up space in their homes to help others.

The couple met with survivors of recent Grenfell Tower disaster, London Bridge terror attacks and the 7/7 London bombings in 2005 (PA/AAP)

The Duke of Cambridge added how he had viewed efforts first hand "on the ground in the wake of the Grenfell Tower fire".

"In the wake of tragedy, managing and channelling the public's desire to help can prove tricky," William noted, adding: "I therefore fully support what you are doing here today."

"We all dread the day when you are needed," the Duke also told the newly formed organisation, saying: "But I know that, like everyone here, I am glad that you now exist".

Prince William and Kate also met with dogs trained to help people in emergencies.

Kate also met with dogs trained to help people in emergencies (PA/AAP)

For the occasion, the Duchess of Cambridge dressed in a royal blue belted Eponine London dress and sported diamond and sapphire earrings that match her engagement ring, where were both previously owned by Princess Diana.

The mother-of-three accessorised the ensemble with patent black heels and clutch, as well as a Women of the First World War poppy brooch.

Prince William also sported a poppy on his navy blue suit - a mark of remembrance to those who lost their lives serving their country.

The couple will attend Remembrance Day services on the weekend alongside Queen Elizabeth, Prince Harry and Meghan Markle.

Prince William was also taken by a particular hound as he met people at the event (PA/AAP)

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